Out-to-in translocation of butanetriol-containing phospholipid analogs in human erythrocyte membrane

Abstract

Fluorescent butanetriol-containing phospholipid analogs were synthesized by replacing the glycerol moiety in 1-hexadecanoyl-2-[6-N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) aminohexanoyl]-sn-glycero-3-phosphocholine, -phosphoethanolamine, -phosphoserine and 1-hexadecanoyl-2-[12-N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)aminododecanoyl]-sn-glycero-3- phosphocholine, -phosphoethanolamine, -phosphoserine by the 1,3,4-butanetriol residue, and their out-to-in translocation in the human erythrocyte membrane studied by 'back exchanging' the outer surface-incorporated phospholipids using bovine serum albumin. The results of these studies indicate that the replacement of the glycerol moiety by the 1,3,4-butanetriol residue in aminophospholipids does not effect their out-to-in translocation in the human erythrocyte membrane. Furthermore, since earlier study by Arora and Gupta (Biochim. Biophys. Acta 1324 (1997) 47-60) has shown that the conformation of the 1,3,4-butanetriol phospholipids possess the backbone conformation similar to that of glycerophospholipids, it is suggested that besides the normal phospholipid polar head-group, a normal phospholipid interface conformation may also be required for the aminophospholipid-translocase interactions.